1. Field of the Invention
The present invention relates to a casing for a recoil starter adapted to start an internal combustion engine.
2. Description of the Prior Art
A conventional recoil starter is disclosed, for example, in Japanese utility model publication No. Hei 2-31576 published on Aug. 27, 1990. Referring specifically to FIG. 4(a), the reference numeral 1 denotes a starter casing within which a shaft 2 is fixed in position. A reel 3 is rotatably mounted to the shaft 2. The reel 3 has a circumferential groove 3a within which a rope 4 is wound under the return force of a spring 5.
A ratchet is mounted to the reel 3 and has a central fixed pin. The reel 3 has a ramp surface and a convexed surface adjacent to its circumferential edge. The ratchet is movable between the ramp surface and the convexed surface of the reel 3. A friction plate 9 is mounted to the shaft 2 and has a guide adapted to guide the pin so that the ratchet is moved in a radial direction.
A pulley 13 is connected to an engine and has a concaved end.
As shown in FIG. 4(b), a plurality of air inlets 15 are formed in the entire circumference of the starter casing 1 for cooling purposes. The starter casing i is secured to a fan cover by bolts 16.
With the conventional recoil starter, when the rope 4 is withdrawn against the return force of the spring 5, the reel 3 is rotated with the ratchet since the friction plate 9 is fixed due to frictional engagement with the shaft 2. The ratchet is moved between the ramp surface and the convexed surface while the ratchet pin is guided by the guide of the friction plate 9. The end of the ratchet is radially moved into engagement with the concaved end of the pulley 13. The pulley is then rotated to start the engine.
After the engine has been started, the rope 4 is released to cause the reel 3 to be rotated in an opposite direction under the return force of the spring 5. The rope 4 is then rewound around the reel 3. The ratchet is also returned to its initial position.
To manufacture such a conventional recoil starter, a circular plate is first subject to a drawing process once or twice to form a cap-like casing. The circumference of the casing is then machined or drilled (normally 20 to 40 times) to form a plurality of air inlets 15 in the circumference of the casing. If the circular plate is subject to a drawing process after the air inlets have been formed, the circumference of the casing, particularly a portion of the casing adjacent to the lower edges of the air inlets 15, is likely to be deformed, broken or torn to a substantial extent. This is because the starter casing can not be expanded or shrunk in a uniform fashion. To this end, the plate must be subject to a drawing process to form a cap-like casing before the air inlets 15 are formed in the circumference of the casing.
Such a known method involves a large number of fabrication steps and is thus cumbersome and expensive.